Heat 6 Tbsp. oil over medium-high heat in a large, heavy-bottomed fry pan. Add onions, celery, ginger, garlic, and apples. Sauté mixture until vegetables become tender and apples become soft and start to break up. Remove pan from heat and set aside, allowing mixture to cool.

Combine remaining ingredients in large sauce pot and bring mixture to a slow simmer over medium heat. Continue simmering until the volume of the sauce is reduced about one-quarter.

While sauce is simmering, puree apple and vegetable mixture in a food processor or blender. Add this puree to reduced sauce. Return sauce to slow simmer and continue cooking until sauce is thick, but can still be poured. If it seems to be too thick, thin it with a little hard cider.